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Does a trent 900 engine have the ability to spin extra or more fans?
Given that the most modern geared turbo fans gear down spinning the fan, which essentially translates to requiring less torque or horse power to spin the fans.  If the gearing down is in the magnitute of (10:1)(correct me if I'm wrong) and comparable engines were able to spin the fans at a higher speeds without gears, how many more fans can the engine spin if there was a modifaction of an additional propshaft to spin the other fans, because there is a gearbox.  How much of an impact on fuel consumption would the be for an extra 1,2,3, and 4 fans if at all it was possible?

So you are saying if you convert a single wheel drive car to 10 wheel drive then the engine can be 1:10 smaller without degrading any capability?

Im saying what is the maximum it can handle because I gather if the engine could spin the wheel without a gearbox that gears down 1:10, I imagine it can spin the all or more than 1 wheel because there is a gearbox

A geared turbofan can spin a different fan at a different speed than an otherwise equivalent non geared engine. But a geared turbofan does not have the ability to spin additional fans at the same rpm, or spin the same fan faster, than a non geared turbofan (if that's what you are asking?). What is required to compress air (by spinning the fan) is shaft power. The level of power provided by the turbine is not increased by adding a gearbox. Indeed, a gearbox adds friction and hence mechanical inefficiency, so the level of power that is available to the fan will actually decrease in a geared turbofan.
HP = Torque (in ft-lbs) x RPM ÷ 5252
A gearbox which reduces rpm, increases torque, but with a slight loss of power due to invetitable inefficiencies.
Your question is quiet confusingly written, but it appears to imply the Trent 900 is a geared turbofan, which it isn't. The Trent is a 3 spool engine, and is the first of the Trent family with a counter rotating HP spool.
The only large geared turbofan in current use is P&W's PW1000G family. (See comment below regard two smaller geared turbine engines). This uses a star design  gearbox to transmit 30,000 hp at a 3:1 ratio. The PW1100G, the largest engine in the family, is a 12.5:1 bypass ratio, and a max thrust of 35,000 lb. In comparison, Rolls Royce is developing their "UltraFan", and is expected to use a planetary design gearbox to transmit 70,000 hp at about a 4:1 ratio. They hope to eventually get to bypass ratio of 15:1, and an overall pressure ratio of 70:1. The thrust for the UltraFan is said to be in the range from 25,000 to 110,000 lbs, so it looks like being a signifficantly bigger engine the P&W's geared turbofan.

Power loss in the gearbox is mostly due to friction, which generates heat. In miniature gearboxes, heat is not much of a problem because the power losses and the absolute amounts of power involved are relatively small. However, it's much more of an issue in large gearboxes which usually require oil coolers to remove the heat caused by the inefficiencies.
Thus, gearbox efficiency depends on friction. This in turn depends on the quality of the gearing, the number of tooth engagements (how many times one wheel drives another) and the load torque (how much "moment" the gearbox has to deliver).
This article says that a spur gear, the type used in geared turbofans, have an mechanical transmission efficiency of about 98 to 99%. If you look at the picture above, you will notice 8 points where the gears mesh, and efficiency will be lost at ech contact point, so needs to be kept to a minimum.
For a comprehensive overview of geared turbofans, see this "flying engineer" article.

The PW1000G is the only large geared turbofan. The geared Garrett TFE731 (most of the Learjets, some Falcons, Hawkers, Gulfstreams) and Lycoming ALF 502 (BAe 146, Avro RJ, CL-600) have been around for 30+ years.

Gearboxes do provide more or less torque at the output end, that is their whole point.

@Koyovis.  Yes, correct. I meant power. Thanks for picking that up!

@user71659. Dead right, I wasn't aware, thanks. I have modified my answer.

A gearbox that reduces rotational speed indeed provides more torque at the output end: half the rpm, twice the torque. This increase in torque can be used for driving a larger fan disk, then possible because the lower rpm means tip speed can stay below critical Mach; or it can be used to drive an extra disk behind the first disk, counter-rotated to compensate for torque and to reduce exit swirl.
Given a choice between driving a larger disk and driving two counter-rotating fans, the preference will always be the larger fan. If tip speed approaches compressibility, simply gear down more. The twin disk scenario will only be explored if practical limitations to increasing fan size are encountered, for instance if the engine simply becomes so big that the landing gear becomes impossibly long.

Are you asking for there to be more compressor stages?
I do not know of any additional intake fans that you could add. There might be a modification to add compressor stages though.
This website might help.
If it is a 10:1 ratio, the Intake fan would spin once with more power than the compressor, but the compressor would spin 10 times for every 1 spin of the intake fan.
Hope this helps!
Charlie :)

This link might also help.
https://www.rolls-royce.com/products-and-services/civil-aerospace/airlines/trent-900.aspx#/


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Where are elevators located in aircraft with delta wings?
Where were elevators located in aircraft with delta wings, notably the Concorde and the Blackbird SR-71?
If they didn't exist, how did these aircraft perform the nose up maneuver mid-air and at take off?  Why didn't they need elevators?
As mentioned in the comments:
While the other question is the same, the answers don't mention the distance between the CG/AC and the elevons (large moment) nor the stabilizing effect of the long delta wing (or the presence of canards on the TU-144). So there is room to improve it.

Between floor 1 and 5?

If you think that there is the need for more details on the other question's answers, you can put a bounty on it. If you think there are more questions to be answered, you can edit your own to be specificallly about something that is not mentioned in those answers.

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text:
What is the diameter of a Trent 900 engine?
What is the diameter of a Trent 900 engine, i.e the diameter of the fans, from one fan tip to the one that is directly opposite it? What is the radius of the fan or the the length of each fan blade?

The Trent 900 fan diameter is 295cm.

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What mechanism or design aspect prevents jet blast from escaping the front of a Ramjet or scram jet?
Enormous air pressures result in the thrust of a Scram jet or ramjet engine, more so the pressure required to drive the aircraft forward at supersonic and hypersonic speeds.  Given that these engines are designed to function without a  fan which sucks air and at those speeds would prevent air from coming in too fast or going back where at came from post being heated.  What mechanism or design aspect prevents jet blast from escaping out the front of a Ramjet or scram jet, resulting in lost thrust and or perhaps negative thrust given that explosive pressure would drive air in any direction that would allow it to escape.
I'm also considering that the air entering the engine does not have that much pressure to prevent this cause if jet blast did exit out at the front, scram jets and ram jets would not be able to produce thrust

Pressure is the greatest just before the combustor in both jet and ramjet engines - therefore air would have against the pressure differential for this to happen (turbine only has therefore an indirect role)

The area of highest pressure before the combustion chamber is called the diffuser...

Primarily the pressure differential between the stagnation pressure at the inlet and the ambient static pressure.  Combustion takes place in an isobaric environment with the enthalpy of the exhaust gases being converted to kinetic energy by exiting the nozzle per Bernoulli’s Principle.  Therefore the pressure differential between the combustion section and the intake vs exhaust nozzle only favors gas flow out the nozzle.

Both ramjets and scramjets work on the principle of supersonic flow: a ramjet has supersonic flow before the intake, and a scramjet has supersonic flow throughout the engine.
When air encounters a disturbance, the pressure created by this travels at the speed of sound. This means that for supersonic flow, any information about a disturbance coming up does not move upstream in the form of pressure. All the incoming air particles are just going about their day, not moving out of the way (remember, by Newton's laws you need a force for something to start moving, and no pressure means no force), until suddenly, there's a disturbance! This is how you get shockwaves.
Now imaging an air particles behind the shockwave in the combustion chamber in a ramjet. It wants to escape, and for that it needs to move either upstream or downstream. Downstream is easy, just go out the back of the engine. Upstream however is impossible.  It could go up to the shockwave, but there it will just get pummeled by unwitting air particles. No matter how much you increase the pressure, the incoming particles have no idea what's coming and will just hit our particle right back.
A scramjet is fully supersonic. There's not even a subsonic particle trying to escape to the front; it may try and form a shockwave but since this shockwave travels only at the speed of sound it will never try and catch up to the scramjet again.

“Both ramjets and scramjets work on supersonic flow.”?  Negative.  Ramjets use subsonic airflow through them.  Ramjets are most efficient for use in supersonic ie Mach 2 to Mach 5 regeimes of flight.

@CarloFelicione Better this way?

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Can electroaerodynamic propulsion be used to circumvent sonic booms?
MIT researchers have created and flown the first plane that doesn’t require any moving parts.

“Although it is still a long way off from commercial gas turbine
  propulsion … electroaerodynamic propulsion has the potential to be a
  game-changer for short-range, small-payload drone flights,” says
  Priyanka Dhopade, a researcher at the Oxford Thermofluids Institute.
Even if this type of propulsion can’t get efficient enough for
  commercial aircraft, Barrett believes it could be used in conjunction
  with jet engines. He says that electroaerodynamic propulsion systems
  can be embedded in the skin of a plane and used to reenergize the air
  traveling along the aircraft. Currently, this air ends up behind the
  aircraft, moving slowly and dragging it back. The addition of the new
  propulsion systems could eliminate this drag and increase fuel
  efficiency.

Can this type of technology be used to circumvent sonic booms. My interpretation is that energizing the air to reduce drag is in effect reducing its collusion with air, which causes noise and sonic boom... In other words reducing drag is reducing air colluding with the airframe hence less noise and sonic boom
I'm not talking about engines but the airframe. The text says: "He says that electroaerodynamic propulsion systems can be embedded in the skin of a plane and used to reenergize the air traveling along the aircraft. Currently, this air ends up behind the aircraft, moving slowly and dragging it back. " My interpretation is that energizing the air to reduce drag is in effect reducing its collusion with air, which causes noise and sonic boom... In other words reducing drag is reducing air colliding with the airframe hence less noise and sonic boom.
For further reading read here:

An electric plane with no moving parts has made its first flight
A powerful new battery could give us electric planes that don’t pollute
A manufacturing trick with magnetic fields produces a battery that may discharge fast enough to get an aircraft off the ground.
Advanced Stellar Propulsion Systems

why do you think that the sonic boom has anything to do with the propulsion system used?

The text says:  "He says that electroaerodynamic propulsion systems can be embedded in the skin of a plane and used to reenergize the air traveling along the aircraft. Currently, this air ends up behind the aircraft, moving slowly and dragging it back. "  My interpretation is that energizing the air to reduce drag is in effect reducing its collusion with air, which causes noise and sonic boom...  In other words reducing drag is reducing air colluding with the airframe hence less noise and sonic boom

no, that's not how a sonic boom works.

I thought sonic boom noise was the result of air colluding with the airframe, the same can be said about drag.  So energising air to reduce drag will also reduce the resulting noise caused by these collusions

@securitydude5 collusion is not a boom.

Collusion creates boom

No. Sonic booms are caused by shockwaves which form on the aircraft structure as it moves through the air, not by the engines. Completely unpowered craft can create sonic booms, for instance the Space Shuttle and other spacecraft on re-entry.
Even if you accelerate the air along the airframe you aren't going to be able to stop the boom, because it's not caused by the air colliding with it. The shockwaves are cause by the compression of air being displaced by the aircraft as it moves through it. It may change the characteristics of the boom, it will be interesting to see if they ever manage to get the technology produce enough thrust.

Exactly. Im not talking about Engines but the air frame .... The text says: "He says that electroaerodynamic propulsion systems can be embedded in the skin of a plane and used to reenergize the air traveling along the aircraft. Currently, this air ends up behind the aircraft, moving slowly and dragging it back. " My interpretation is that energizing the air to reduce drag is in effect reducing its collusion with air, which causes noise and sonic boom... In other words reducing drag is reducing air colluding with the airframe hence less noise and sonic boom

You need to make this clear in your question @securitydude5.

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Is it possible to calculate possible fuel savings of known turbofan engines if operational heat could be increased
Starlite is liquid paint like substance invented in 70s and perfected in the 80s by the late British inventor Maurice Ward (1933-2011).  It is said to be able to withstand heat from 78 nuclear explosions.  It can be coated on numerous applications requiring heat resistance namely aircraft engines, and can function without losing its structure or heat resistance properties withstanding heat of up to 78 nuclear explosions.
Is it possible to calculate possible fuel savings of known turbofan engines if operational heat could be increased to starlite insulation temperatures
This question is not spam please vote to reopen it.
It is basedon the relationship between heat or running engines hotter achieving fuel efficiency.  The current drawback to achieving higher fuel efficiencies by running engines hotter has been materials operating at their thermal limits which is quite phenominal for achieving this feat.  Praises to the scientist and engineers who have relentlessly taken efficiencies and materials to their safe operations limits, and further praises to materials scientists for your unrelenting work in discovering new materials that make for a better world like Stalite.  New discoveries like Starlite could take efficiencies to higher levels in this day and age of pollution and higher oil prices and finite oil resources.  Such discoveries discussions and questions are good for aviation and for this site.
This question is not spam please vote to reopen it. let us defeat the close bregade
For further reading
read here,
What is Starlite
How does the 'wonder material' Starlite actually work? - BBC Reel

Been gone a while please do not close this question, many people could learn a lot from the answers

I think if you focused on the question in the title, and avoided the salvation of jumbos (probably opinion-based) and the dubious "78 nuclear explosions" starlite bit, I think you'd have a better question.

I'm voting to close this question as off-topic because it appears to be spam thinly disguised as a fuel-efficiency question.

@Sean all links are from the BBC. We cannot find any sign of spam here.

The Close bregade has conspired to close question again. This kind of behavior is a good example on how democracy online can be used as a tool for abuse.  Or perhaps you people afraid your competitors might discover there is Starlite as you have just discovered and hence voted to close the Question?

The fact that you think this site competes with Starlite isn't doing you any favors. If you want this question reopened, I would remove the sales-pitch stuff (e.g. "praises to") and focus on an actual question. You have a lot of text here that isn't asking anything, and is saying how awesome over product is. That sounds like spam to me. Focus your question on a question, and you'll have better luck with "the close brigade."

The fact that you interpret the comment as the site competing with starlite is perplexing.  This site should not be about explanation on concepts you struggled to grasp at engineering school only but invention and discovery, that human beings and this civalization  improve continually, once you grasp that you and the close bregade  will not interpret any innovation questions as spam

Here is why any painted-on coating will not have the benefit you seek.
After a jet engine has run long enough to reach normal operating temperature, its turbine blades are not just hot on their exterior surfaces- the heat they are exposed to has soaked into them and they are hot all the way through. To resist the tremendous stresses they are subject to, those blades must be strong not just at their surfaces but all the way through as well.
For a thin coating to successfully protect a turbine blade from long-duration heat exposure, it would have to possess zero thermal conductivity, which is impossible for any solid made of ordinary matter- including Starlite.
In stark contrast, the thermal loads imposed on objects exposed to atomic bomb  explosions are so brief in duration that there is no time for even a thin coating of paint to conduct that incident energy to the metal underneath it. And the magnitude of the thermal pulse is so great as to simply vaporize the paint, leaving the metal underneath intact. High-speed movies of things like buses and trucks exposed to the thermal pulse of an atomic explosion show this effect very clearly.
This means that whatever Starlite is made of, its purported resistance to exfoliation and vaporization in response to a millisecond thermal pulse are of no utility at all in protecting metal parts which must withstand tens of hours of exposure to high temperatures.

The point is minimum conductivity.  That minimum conductivity protects against heating even from compression.  That is the function of insulation.  It prevents the heat from soaking into them in the first place.  If it does, soak into them, it will do so at the most minimum rate.  See the egg experiment in the link

From the BBC videos you clearly see that the material expands when heated.
This is something you don't want in a jet engine. If your engine changes shape, and reduces the available cross-section for air to go through, your efficiency cannot do anything else than go down.
Said otherwise: coating the interiors of a jet engine is not the ideal application for Starlite in its current form. If in the future the Starlite formula will be released and improved in such a way that the material won't expand unpredictably under intense heat, then this might be an application worth considering, but until then it remains pure speculation, since we don't know the real limits of the material (such as thickness required for the coating to be effective, resistance of the coating to prolonged exposure, etc.)

Thank you for the answer but I'm sure as a last resort though, and all attempts to use starlite in jet engines without modification are exhausted, jet engines themselves could be modified to expand at temperature to accomodate starlite, in turn exploiting the resulting efficiencies from running engines much much hotter

@securitydude5 that's once again in the realm of speculation, so I won't discuss that further.

Random expansion of parts that are fitted in extremely close tolerance to each other is also a Bad Thing™.

@Federico Attempt to Modify Starlite we shall then

Thermodynamically, you can calculate the efficiency of a Brayton cycle engine (gas turbine) based on the difference between the peak "hot" temperature and the exhaust temperature ("cold" temperature), assuming you don't change the pressure ratio between atmospheric and engine maximum.  Increasing the (absolute) temperature ratio between burner and exhaust with other factors held equal will increase the thermal efficiency by a similar ratio.
That's very difficult to do, however.  Kerosene only burns so hot, and modern engines do a good job of protecting the turbine blades from the heat -- adding a heat rejecting coating would gain very little in terms of burner temperature, hence add little to efficiency.  Most recent improvements in efficiency in gas turbines have revolved around running the burner at higher pressure, and finding a better compromise between exhaust mass flow and exhaust velocity.

"Kerosene only burns so hot" What do you mean there? You mean that the reaction rate decreases with increasing temperature?

@Sanchises no, any fuel-oxidiser reaction has a maximum temperature, reached when you have a stoichiometric relationship between the two. that's because temperature is energy, and there is only so much energy you can extract from a specific reaction, and the maximum is when you have stoichiometric ratios.

@Federico But the compression can add (in theory) arbitrary amounts of energy. So my point is that the combustion chamber temperature is not limited by the kerosene burning temperature in atmospheric conditions.

@Sanchises if you really want to go that road, autoignition of the fuel will put a hard limit.


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How can a passenger determine airspeed without a handheld GPS?
This question is in the context of being a passenger on a commercial airliner, where you're in the cabin and the cockpit door is locked.
In another question, someone posited that if an airliner had reduced its airspeed by 60%, he'd be quite concerned.   I asked "How would he even know?"
How would a passenger on a commercial airliner, who is reasonably technically savvy but not a pilot, be able to discern airspeed?
This is old school. The person does not have any modern smart devices.  Or does, but their battery ran down.  (Not looking for a product reco for a gadget or app, there's another answer for that.)  The person could probably improvise a plumb bob, stuff like that.
Would anything change if the passenger has a clear view of the ground, relevant maps with scales, and a stopwatch (but not any wind data)?

Possible duplicate of How to determine aircraft altitude and speed, as a passenger?

@pondlife that one is asking about mobile apps, and is seeking a product reco which is off-topic.  I'm asking old-school.

With some experience, isn't it possible to form a rough idea from engine and wind noise?  I could certainly tell when an airliner reduced speed significantly.  It does work pretty well for me, in the roughly 50-150 kt range of single-engined prop planes.

@Harper OK, thanks for updating the question to make that point more explicit!

It is impossible for a passenger to determine the airspeed to any reasonable accuracy (otherwise Birgenair 301 and Aeroperu 603 would not have crashed).
From my personal experience, it is not possible to receive GPS signal using a handheld-device in the passenger cabin. Even if it works, winds aloft at cruising altitude are often in the range of 100~200 knots. That throws the calculation completely off even if ground speed is known.
The only reliable way is to refer to the entertainment system, which obtains its data from the cockpit and is therefore accurate. However, the interface is usually programmed to display measurements in other units; the indicated airspeed has to be calculated from the displayed values manually.
Here are some ways you can guess the airspeed to a certain extent:

If you do not notice any significant airframe vibration, you can
assume the airspeed is somewhere between the stall speed and the max
airspeed.
If you can tell the flaps position from observation, you can also correlate that with the usual flaps extension speed of the model
you're flying, which should give you ~20 knots of accuracy.
If you are familiar with the SID or STAR of the airport, and you know planes normally pass a certain point at a certain speed.
If you have a handheld ATC receiver, sometimes ATC will issue speed instructions to planes during approach.

If you do not notice any significant airframe vibration, you can assume the airspeed is somewhere between the stall speed and the max airspeed. - this is the best sentence I've read today

Isn't there something about consumer GPS receivers being required to be artificially limited in how high speeds they function at? (I don't remember what the cutoff speed was supposed to be.) That could conceivably cause difficulties even if you could get a good signal within the airplane.

Michael - CoCom limits civ gps to about 1200mph. Probably not an issue on most airliners :-)

I've recorded my flights with all my handhelds with GPS, and it works perfect on a window seat and good enough on the next. my first phone sometimes  had trouble with altitude, but my current one gives accurate data (validated with on board entertainment system)

Same for me, as sweber says. I use Maps Me on my phone, on a window seat, very often, and never had an issue. And the track is very precise, as I was able to confirm many times when the map was showing me the aircraft approaching the runway during landing.

@Michael Kjörling: Long time ago, 1990-s, civil GPS units were limited to 99 knots.

With no wind data and no knowledge of how the aircraft is configured or being flown I don't see how you realistically can.
In theory, if you could guarantee the aircraft was at a constant airspeed you could monitor groundspeed across legs in different directions - but in reality you aren't going to be on an airliner that's flown like that.
For example, if you went North at 500mph (Ground Speed) and South at 550Mph then we know the wind had a tailwind component on the second leg and I'm sure there's some clever maths somewhere to help you work some degree of it out but it'll be inaccurate by some margin.
You can't even really tell from the engines without access to instruments because you're not going to have pitch data.

For a constant load, air density, Cl and wing area (no flaps deployed...), AoA and airspeed are correlated. If the horizon is visible, a passenger might (in theory...) determine the angle between the fuselage axis and the horizontal and thus estimate the airspeed.

It's pretty much impossible
We can sense changes in our velocity - accelerations - but unless we were equipped with sensors and instrumentation (and sadly, we are not) able to calculate velocity from cumulative changes in velocity, the best we can do is note that we are speeding up and slowing down.
I say "at best", because even that is hard. If you're strapped into your airliner seat and the is pitched up or down, you will often have a subjective experience of speeding up or slowing down, simply because of the way your body shifts in its seat.
(Motion simulators make use of this, tilting the platform to provide a sensation of acceleration.)
And, in any case - it's useless. You want airspeed, and you'll have absolutely no way of knowing that just by working out what your ground speed is unless you also know what the wind is doing (i.e. to answer your final question, no amount of map and stopwatch cleverness is going to help you either).
But wait!
However: depending on your aircraft, it might be that in order to sustain level flight at a certain altitude in a certain configuration, it must fly at a certain minimum speed.
So, if you were armed with some flight envelope data for the aircraft, and you had altitude information (that would have to be barometric altitude, and I'm not sure where you're going to get that from), and you were able to  discern the plane's configuration (deployment of flaps and so on) you might possibly be able to judge that the plane's airspeed must be at least such-and-such.

[...] and you were able to discern the plane's configuration (deployment of flaps and so on)[...] really? you would guess the lift of the airplane by checking your flaps? Can you tell the degrees? and how you know the downforce on the tail? (Yes I am just poking you)

@,Alexandros The degrees are often marked on the flaps themselves, see e.g. https://goo.gl/images/goS9pi

Airspeed is going to be hard, if not impossible: you cannot stick your hand out of the window and don't have a connection to an outside transducer like the cockpit instruments have.
Ground speed is a different matter. I have successfully used the GPS transducer on my phone to measure ground speed on board of an aircraft while travelling as a passenger; there was a question about this on this forum some years ago. And ground speed will give at least an order of magnitude, yes you need to superimpose jetstream velocities which you can't measure, only estimate.
And accelerations can be detected by the biological transducers inside our head. They have limitations, tend to be desensitised after some time of perceiving a constant acceleration, don't detect small rotational accelerations etc. Too confusing and inaccurate to use as a reference on board an aircraft, which is what all IFR instructors keep saying as well.
So the best bet is to measure ground speed and add an educated guess on wind velocity.

You could use a sextant! Your airspeed would be more averaged as it takes minutes to even start getting a bead on your current position.
There is an article in Air Space Magazine that explains the basics. Note that to get even 1 position with all the movement of the aircraft takes a few minutes

But acceleration of the aircraft and turbulence frequently deflect the true vertical; therefore, a single reading may not be accurate. For that reason, the bubble sextant also has a mechanical averager with a wind-up clock. It takes 60 altitude readings over a two-minute period, using a little counter that looks like a car’s speedometer to average and display the measurements.
Once I know the the star’s altitude, I can find where I am on an imaginary line extending from me toward the star’s geographic position. But finding the altitude of the star is the second step in plotting my position.
The first step is to assume a position, a set of coordinates I determine by deduced, or dead, reckoning. Based on three pieces of data—this assumed position, the altitude of the star, and its azimuth (its angular distance from true north), I calculate where I am by proving that I’m not where I assumed!

There is also this other stack question which has a neat explanation of the sextant port in the older VC10!
Now you say, " I can see the stars but we're flying over clouds!" well a captain in London came up with an artificial horizon attachment for his sextant described in Scientific American

An artificial horizon is provided which consists of two bars that exactly span the periphery of the sun's image in the horizon glass, and are maintained in horizontal position by means of a pendulum forming part of the attachment

though as the one commenter noted the graphic was not attached to the article...
Now would you know immediately about the power change? Probably not without using the other answers listed. BUT you may be able to confirm your suspicion over the course of say, 20-30 minutes if you were getting a position every 2-3 minutes.
Caveat: Also the star you'd be using would have to be on the horizon or risk poking a hole in the ceiling of the plane

That method would allow you to determine the ground speed, not the airspeed. For an airliner flying at cruise altitude, the difference can be very large...

@xxavier absolutely right. I hadnt thought of that distinction when writing it. Maybe I'll update to include a weather balloon for winds aloft...

Estimating airspeed is difficult. Perhaps possible but it requires a lot of knowledge. You can figure out your altitude and whether you are level from outside references. From the deck angle you can estimate the pitch angle and from there the angle of attack. You can cross check this estimate by viewing the horizon. By estimating the number of passengers you can estimate the weight of the aircraft. Combining these two numbers gives you an estimate of the equivalent airspeed. Combining this with the altitude and assumed ISA temperature gives you an estimate of the true airspeed.
This estimate would be very rough. But a reduction in airspeed of 60% would be very, very noticeable. At 60% less airspeed you need roughly 4 times the angle of attack to maintain the same amount of lift. With a normal cruise angle of attack of around 3° and no configuration changes, this would correspond to a pitch up of 9°. This is a fairly steep deck angle- easily measurable and taking a moderate effort to walk up.
In short, estimating the airspeed is possible but getting a precise answer is difficult to impossible. Detecting very large changes in airspeed is much easier. A 60% reduction in airspeed is roughly the difference between normal cruise speed and final approach speed for a typical airliner. Configuring for final approach is usually very noticeable on an airliner, and if the same speed is reached without reconfiguring, the airplane is going to be at a high pitch angle and probably perilously close to stalling.


text:
What does "28 volts DC" mean, really?
The common battery voltage on aircraft is commonly referred to as "28 volts".   What does that really mean in terms of a lead-acid battery?
In many uses, such as cars ("12V"), trucks ("24V") forklifts and golf carts ("36V" or "48V"), locomotives ("64V"), the nameplate number is exactly twice the number of lead-acid "cells".   But in reality, the fully charged/charging/float voltage of the system with alternator running is higher - cars 14V, trucks 28V, locos 75V.
Battery units are generally sized at 3, 6 or sometimes 4 units (6, 12 or 8 volts nominal).
So, when aircraft power is specced at 28 volts -- do they actually  mean a 14-cell lead-acid battery or  two 7-cells (which is almost unheard of)... or do they actually mean a 12-cell battery with a "float" voltage around 28V, (built out of two common-as-dirt "12V to everyone else") batteries?
I hope this isn't overloading this question too much, but when nickel-cadmium packs are used, does that have 20 cells, or 19 or some other number?

It's the second option. In any other context, a small aircraft's electrical system would be called "24V". But the alternator regularly puts out 28V, so that's what's typically expected if you hook up your multimeter while the engine's running. Of course, the on-board equipment can operate over a wide range of voltages, often down to as little as 20V.

Actually a lot of TSO'd equipment covers a 12-28 voltage range because some aircraft have 12V (14V) systems and they typically make them to be compatible.

@HiddenWindshield  I agree.  The USN H-60 battery in a perfect world would be a 35v battery.  So, it will put out right about 28v when it has a good charge.

@Ron Beyer: Some aircraft?  Probably most, especially if you leave out military and airliners.

This makes it clear enough, just a differnet convention: it's like if a niche of electrical engineers decided to call the electron source +, and for legacy reasons they stuck with it.  Or the way (for reasons) aviators say their speed is 350kias when it's actually 500mph.

Anedoctally, I've hooked two 220V to 110V transformers in series and then powered a PC with what was basically 55V AC. The computer powered up and displayed the BIOS messages, albeit sluggish. The worst that can happen with underpowering a device is that it fails to function but most do.

@Mindwin Your last sentence is absolutely false. Undervoltage can and has caused damage to computer equipment. That is, after all, why undervoltage protection devices exist. As an aside, I'm really surprised that your computer was sluggish at a lower voltage. After all, computers aren't like motors where the speed depends on power. Computer speed is regulated by a crystal oscillator. The only explanations I can think of is either it took longer to charge the power supply capacitors to boot, or it was overheating and auto throttling the clock speed to protect itself.

@Mindwin I have a ton of experience with PCs, and it doesn't work that way. SMPS will produce completely consistent output voltage at any input voltage. It's possible a 100-250V SMPS would work with a 55V input (usually they want at least 70-ish - but since 220V is really 230-250V, you likely had ~60V), but if it can't give enough power, it will fail to produce any. The PC would frequently power down, NOT work sluggishly. ATX power supplies do not inform the load about how much power they can supply. The load will draw everything until it goes off.

@Harper - Reinstate Monica: 350 kts = 402.8 mph :-)  And there's a major difference between transformers and switched-mode power supplies - the obvious difference being the weight of heavy old wall-wart transformers vs newer & lighter SMPS chargers.

@jamesqf I said kias not kts.  You're in the right place to ask what the difference is :)

@Harper-ReinstateMonica: KIAS are knots; Knots Indicated AirSpeed. If the intent was to compare indicated airspeed to true airspeed or ground speed, comparing knots to MPH doesn't convey that very well.

@therac if memory serves, it was a couple decades ago. And the OS (win95 I think, we were going to play Diablo in LAN) never booted. As I said, it was sluggish in the BIOS screen.

@Mindwin OS not booting is more expected. Not sure why BIOS would be sluggish, the CPU only has one clock rate for it. My guess is that it could be "distracted" with devices failing on the buses, while the CPU's voltage regulator pulled it through. Anyway, insufficient voltage or power can be quite dangerous to electronics - often the best thing that can happen is that they simply don't function. Undervolted SMPS and voltage regulators can deliver power in pulses, on/off - hello surge currents and AC in your DC circuits.

@Harper - Reinstate Monica: I know what the difference is between airspeed in knots (kias) and mph (indicated, which is what you get if you fly an older Cherokee - the airspeed indicator is labeled in both).  The difference between air speed and ground speed is something else, whatever units you choose to use.

@jamesqf good to hear, because your initial criticism seemed to be unaware of the difference.

@Harper - Reinstate Monica: Then I didn't word it properly.  Thought it was obvious that I was just pointing out a math error.

Multiple sources indicate that the 28 VDC bus on aircraft powered by 24 VDC batteries, and the 24 VDC systems on truck powered by 28 VDC alternators, are basically the same thing, and that is is just a naming convention.
The number of cells is a function of the nominal voltage and the cell type. From this site:

Lead Acid: 2 volts/cell
Nickel based for aviation: 1.25V per cell
LiIon: 3.6 V per cell.

For instance, from this site on the B737:

Batteries
Battery - Is a 36 ampere-hour, 24 volt, 20 cell, Nickel-cadmium battery and should provide 30 minutes (20 mins 1/200's) of standby power if all other generators fail.
Aux Battery - This is a reserve battery on the NG/MAX which is normally isolated unless the main battery is powering the standby system when it operates in parallel with the main battery. The aux battery combined with the main battery will provide 60 minutes of standby power.

The 28 VDC bus on aeroplanes is normally powered by a Transformer Rectifier Unit (TRU), which is powered by the 115 VAC bus. Power is transformed first from 115 VAC to 28 VAC, then rectified from 28 VAC to 28 VDC. The charging voltage must always be higher than the nominal battery voltage.
From the same B737 site, indicating that the average voltage is more in the order of 27 VDC:

The purists may like to know that the DC voltages are measured at the following points:

True Blue Power's Li-Ion batteries have a nominal voltage of 26.4 VDC (3.4 V/cell) with a 28 - 28.8 VDC charging voltage. https://www.truebluepowerusa.com/products/aviation/advanced-lithium-ion-batteries/tb20/

Let me start of with two facts that pretty much answer your question:

A 24V battery is a battery that can output at least 24V over the majority of its capacity.
To charge a rechargeable battery you need to push charge into it by providing it with a higher voltage than what the battery is currently at.

To put a bit more meat on, here is a typical discharge graph for different types of 48V batteries (I could not find one for 24V, but divide the y-axis voltages by 2 and it will be pretty spot on):

So, you design your circuit so that it can stay alive on the minimum-rated voltage from your battery (24V, in your case), but also so that it can handle the voltage that the alternator has to put out to keep the battery charged (for a 24V battery: roughly 28V), which is what it will be at most of the time.
Btw, to directly answer your question:

So, when aircraft power is specced at 28 volts do they actually mean a 12-cell battery with a
  "float" voltage around 28V, (built out of two common-as-dirt "12V to
  everyone else") batteries?

Yes, two common-as-dirt 12V batteries with a float voltage of 28V.

Dividing the 13 LiMnO₂ cells by half might be problematic.

@Pete, dividing by half is easy; it's dividing by two that you'll have problems with.  ;-)

But in reality, the fully charged/charging/float voltage of the system with alternator running is higher

Yes. If a car battery states 12V that's kind-of the lower limit. As in, it really shouldn't drop below 11.8 when fully discharged, although depending on the type of battery and vehicle it may still function (for some values of function). A fully charged lead-acid battery goes 10-20% above what's on the label (in case of 12V accu, up to 14.4V is not uncommon).
While the battery is being charged, the voltage is going to be even higher. An alternator for a 12V system will probably output 14.5V. External chargers can go above that. After all, charging tends to go faster if there's a higher-than-target voltage connected. I've seen 12V chargers charging at 15V, but that's probably not very good for the lifespan for the battery involved.
When a voltage is specified on a battery, consider that voltage to be what's left when the battery is almost drained. So everything connected to it should be able to handle voltages that are higher or switched-off during charging (the latter is uncommon in my experience).
This is all assuming lead-acid batteries. Newer batteries are trickier.


text:
How do seaplanes do run-up checks without brakes?
Usually on run-up you want to check the response of the motor when changing for example the carb-heat (if existent). At least we did so on my intro flight (yey!). To prevent us from rolling onto the active runway we (obviously) held the brakes.
Now I wondered how pilots of floating planes and flying boats prevent movement on pre-takeoff checks. Additionally most images I found from flying boats they usually have more than one engine. Similar question here: How do pilots prevent swimming circles as one engine is started and the other(s) is/are not?
I scanned this FAA document from this related question but that is mostly is about landing (which is interesting as well but I assume that as in the linked question the airframe and especially the water resistance take care of that).

Drop anchor. /obligatory

Eventhough the water would (likely) not be very deep where the planes dock pulling in the anchor would take time where the plane would already be on the go. I am unsure how safe that might be.

@geisterfurz007 - the /obligatory at the end was added to indicate humor. Obviously, it wasn't sufficient - my apologies.

My bad. I am not far enough into aviation (especially seaplanes) to directly see the humor in that and rather took the obligatory as a way of saying "why would you not come up with that". Might be missing social skills on my end tho ;)

@FreeMan: Isn't this why we have the smiley? ;-)

I'll limit my answer to single-engine seaplanes as I've never flown a multi-engine seaplane.
Typically there is no need to stay stationary in the water when doing a run-up. Just do it while taxiing to your takeoff path, or you can do it on your takeoff path. If the takeoff path isn't long enough to do the run-up and then continue along the path for the takeoff, you can turn around, taxi back along the takeoff path, and then takeoff.
At typical run-up power settings, if you hold full up elevator, the airplane will simply mush along on the water since you won't have anywhere near enough power to get it up on the step. In other words, you won't be going very fast.
When giving floatplane instruction, one of the first things I tried to impress on students was to not think in terms of the constraints of straight, hard-surface, defined runways, taxiways and the like. There's no need, typically, to taxi in a straight line, make well-defined taxiing turns, and no need to takeoff in a straight line. Once away from the dock or beach, the airplane is going to weather vane unless you actively oppose that, and that weathervaning is going to have a component caused by the current, if any, of the water you're on.
In my experience, most of the time the takeoff path was either dictated directionally (a river) or pretty much wide open (lake or reservoir). For new students in my area, reservoirs were preferred. More often than not, it was a matter of getting a short ways off the dock, do the checks other than the run-up while moving away from the shore at a 90 degree angle more or less, lift the water rudder, bring the stick all the way back, and do the run-up, all the while letting the aircraft weathervane into the wind. Then just takeoff.
I never flew a twin-engined seaplane, but I see no reason why you couldn't bring both engines up to the run-up rpm, do the checks on one and then the other. While checking the mags, carb heat, and props, there would be a little asymmetrical thrust, but not enough that the rudder couldn't handle that.

Aircraft on ski's have the same problem, and the answer is relatively simple... They do an abbreviated run-up on the go.
Even if the aircraft has a constant speed propeller, many can't feather the propeller enough to completely prevent motion. There are a few piston light aircraft that have a feathering prop, and one that I know of that can actually reverse.
This takes some practice, to be able to throttle up to your run-up RPM, do a mag-check, carb heat check, and prop check (for constant speed), but can usually be done in less than 30 seconds, or as little as 10-15 seconds for an experienced pilot. The hard part is dividing your attention between not running into anything and completing your checklist.
Remember, it actually takes quite a bit more power to get an airplane moving through the water than it does to move it on land. Some float equipped airplanes have problems taking off from glassy water because they don't have enough power to get up "on the step", or planing the floats (so they have to run back-and forth over their wake to get up). So while 1700 RPM on land basically means you'd be taxiing at 40 knots, on the water it is much slower, and doesn't accelerate as fast.

Glassy water would have been one of my suggestions - it may not stop you from moving, but it'll stop you from taking off!

The Husky backing into the hangar was awesome!

Someone's gonna anchor the plane in place and use it as a gigantic fan...

That runup on the go is also useful for dirt strips (or dry lake beds &c), where holding a fixed position gets dirt in the prop - or so I was told, anyway.

Float planes have variable pitch propellers, meaning that the propeller blade can be angled so that it does not provide any forward movement at all, or even turned backwards so it pushes the airplane backwards a little bit.
When the engines are started, or during run-up tests, the propeller pitch is set so that it does not provide any thrust.
When flying, the propeller pitch is adjusted to provide differing levels of thrust for take-off, climb, cruise, or descent.

This is not necessarily true.  Large turbine powered seaplanes can do this but there are plenty of seaplanes with a fixed pitch prop.

I've flown a Super Cub on floats, and it did not have a controllable-pitch prop. Runups were performed while plowing.

Does this lead to higher revs because of not having much load on the prop?  (i.e. less resistance to the engine because the prop isn't moving much air).  Is this an actual problem, or do you just keep the revs in check by not opening the throttle as much?

@PeterCordes That sounds like a decent separate question. Why don't you post it as such?

@MichaelKjörling: A quick search found [an answer]((https://aviation.stackexchange.com/a/12111/7767) for one specific plane: Avoid operation in feather above 66.6 % TQ.  GROUND OR FLIGHT OPERATION If a propeller is involved in an overspeed or in an engine overtorque refer to the propeller maintenance manual.  So as I suspected, yes you can damage things if you open the throttle with the prop feathered, at least on some planes.  If someone else wants to write this up as question, feel free.

Answer 1: WATER RUDDERS
As to your question about the "swimming circles" the answer is that the floats have deployable rudders that provide directional control of the aircraft when in the water. They should be retracted before take off as they can be damaged at high speed. They are linked to rudder peddles so you just use a little opposite rudder, if needed, when you have asymetrical thrust situation.
Answer 2: RUN UP during TAXI
The run up can be performed while "plowing." Plowing is a method of taxing a seaplane that produces a lot of water drag on the floats--basically its a tail low position. The pilot can further encourage this nose high attitude by applying full back pressure (up elevator). This accomplishes increasing drag on back of floats and keeping the nose as high in the air as possible, because water can do serious damage to a propeller at high RPM.
According to the FAA's Seaplane manual FAA-H-8083-23 (Ch4 p.4-12):

"All checks are performed as the seaplane taxies, including the engine
  runup. Hold the elevator control all the way back throughout the runup
  to minimize spray around the propeller."

You've probably seen this poor Grumman Duck being expertly abused
https://www.youtube.com/watch?v=aED7xvYbMfw&t=8s  I both marvel and cringe every time I watch it. I don't know how accurately the soundtrack reflects exactly what the throttle settings were on the day.

@mackk "This video is no longer available due to a copyright claim by NHM IP Rights Limited"   sadly.

@ Criggie, it was a sequence from the 1971 film Murphy's War  set in WW2 where Peter O'Toole's marooned merchant seaman tries to teach himself how to fly the Duck to extract revenge on the German submarine that sank his ship. Well worth watching the whole film if you can find it. https://youtu.be/S-HsRQ46rpA?si=mazYbF-nC3rN_iju


text:
I overboosted an engine in a Mooney 231 - do I need to do an inspection?
I have an intercooler, but no wastegate. Manifold pressure was not controlled on takeoff and went to 50. The max is 37!  If overboosting doesn't really exist because the relief valve opens, then how did the gauge even get to 50?  It was at that level for 20-30 secs. The engine appears to run great afterwards.
Is there anything that should be inspected or done?

Did you happen to note the rate of climb???  Just curious.

This most likely warrants a call to Don Maxwell the veritable Mooney expert but I would for sure have the engine checked by a Mooney expert or someone that knows their way around the TSIO-360-GB. At the minimum a compression test and possible borescope check is in order.
If you have the early 231 in its original config you have a fixed waste gate that can be over boosted on takeoff.

The engine also had a fixed wastegate in the exhaust system, meaning
  careful pilot technique was required to keep from over boosting the
  engine on takeoff.  If the pilot inadvertently added full throttle for
  takeoff or a go-around, the engine would over boost, with only a
  mechanical pop-off valve in the induction system to save the engine
  from literally coming apart on the runway.  Fixed wastegates also mean
  high turbocharger speeds (RPM) at altitude, which reduces turbocharger
  life

I don't know much about the gauge itself but it may warrant checking it to make sure it is operating properly.
You can also reach out to continental and ask them what the over boost limit is. There is a chance they have some data on it or can let you know of a good course of action.

The relief valve may have failed.  It's advisable to have that engine inspected as that kind of overboost can cause severe detonation and damage the engine.  This may mean a complete tear down of the engine.  I'm not an A&P by any means but I think that's want they're going to advise.
Or you could simply have a bad manifold pressure gauge; have that inspected first; it could save you a lot of money.
Did you encounter additional symptoms i.e. Engine really running at a high pitch, possibly with knocking accompanying it?

WHAT?  50" for 20 seconds???  That's nuts!
The first call should be to CMI.
The engine user manual directs a user to see Continental Service Bulletin M67-12 after operation in a sustained overboost condition.  I would say this event qualifies!
Read the SB, call CMI, and then call an engine shop.

Your document link just redirects to the main Continental site...

I'll deactivate the links but the message is the same. CMI has guidance on how to proceed. Either search online, email, or call the manufacturer for more information.

Here's M67-12, but all it says is "call CMI".

I would say that you should definitely have the engine inspected.  I had  a P337 skymaster with two of those TSIO-360s, though mine had automatic manifold pressure control so overboosting was less common.  The manual said an inspection was necessary for even a short overboost of 4 inches if I remember correctly.


text:
How many hours of test flight does a general aviation aircraft go through before delivery?
I'm curious if anybody could give any indications as to how many hours of test flight a factory new small general aviation aircraft* goes through before customer acceptance and delivery.
(Not initial certification, but what is necessary for every new production airframe)
*e.g. Cessna 172, Diamond DA-42 or Robinson R22

All manufacturers have a quality system in place, and they also have a production baseline (which is a result of certification). so, as long as the quality system is utilized, there is technically no need to fly each manufactured airplane. Type certification validates the production baseline (and that each manufactured plane is within the tolerances acceptable for the certification authority or requirements).
However, depending on company manufacturing know how (or lack of) there might be several ground tests (structural, engine, systems checkout) before delivery.
On the other hand, for many military aircraft there's a factory checkout flight, to check and confirm the performance of each frame and propulsion system. This is more useful for risk reduction (to avoid customer complaints and to check the complex system in the air).

There is no regulatory requirement. It must be legally airworthy before any flight including its first one. Most flying done before delivery is to reposition aircraft to dealership or mod center.


text:
Should people flying UAVs be called "Operators" or "Pilots"?
I'm wondering if there is any formal/official definition* pertaining to the title given to people controlling Unmanned Aerial Vehicles? Are they "more" correctly titled Operators or Pilots?
*As set by ICAO, EASA or FAA for instance.
Examples:
The Guardian: "Life as a drone operator"
Air Force Times: "Enlisted drone pilots? Decision expected early next year"

I've had a look through EASA Directive 2009/48/EC where it states:

Operator shall mean any legal or natural person, operating
  or proposing to operate one or more aircraft;

That does not provide a distinction between the entity organizing (e.g. airline) and the actual person doing the flying. A commercial pilot will not title himself an "aircraft operator" but will call themselves a pilot. This is less well defined with UAVs.

To add to any confusion the term "operator" has a specific meaning in aviation as described in this question

“Should” calls for opinion.

@CGCampbell, I hear what you are saying, but what official agency should be considered the source of truth for a non-opinion based answer?  To paraphrase the question:  Official agency "A" calls them pilots, Official agency "B" calls them operators, what do you think they should be called?

The oxford dictionary defines pilot as:

A person who operates the flying controls of an aircraft

So, technically, the drone operator should be called a pilot.
FAA National Policy Order 8130.34C Airworthiness Certification of Unmanned Aircraft Systems and Optionally Piloted Aircraft Section 6 specifically calls the person operating the UAS (only if it has been issued with an airworthiness certificate ) Pilot.:

UA Pilots and Observers.

a. PIC Roles and Responsibilities.

(1) The PIC must perform crew duties for only one UA at a time.

(2) All UA flight operations must have a designated PIC. The PIC has responsibility over each flight conducted and is accountable for the UA flight operation.

(3) The PIC is responsible for the safety of the UA as well as persons and property along the UA flight path. This includes, but is not limited to, collision avoidance and the safety of persons and property in the air and on the ground.

(4) The PIC must avoid densely populated areas and congested airways in accordance with § 91.319.

The order requires the PIC to have a minimum of FAA PPL:

b. UA PIC Certification and Ratings Requirements.

(1) The PIC must hold and be in possession of, at a minimum, an FAA private pilot certificate, with either an airplane, rotorcraft, or powered-lift category; with single- or multiengine class ratings, appropriate to the type of UA being operated.

(2) The PIC must have and be in possession of a valid second-class (or higher) airman medical certificate issued under 14 CFR part 67, Medical Standards and Certification.

UK CAA also talks about 'Pilot Qualifications required to operate Unmanned Aircraft'. ICAO also uses the term 'pilot' for people controlling an UAV.

Both USAF and RAF call the UAV operators pilots- RAF calls them Remotely Piloted Aircraft System Pilots and USAF, Remotely Piloted Aircraft Pilots and they do get the 'wings'

"United States Air Force Unmanned Aircraft Operator Badge" by SSgt Austin May of the USAF - http://www.af.mil/news/story.asp?id=123170151http://www.mildenhall.af.mil/news/story.asp?id=123170577. Licensed under Public Domain via Commons.
However, there has been no UAV pilot license issued as far as I know. The FAA issues a Remote Pilot Certificate, which is required for all non-recreational UAS flights. For exempt recreational flights, a remote pilot certificate is not required; instead, it is necessary to have passed "The Recreational UAS Safety Test" (TRUST). An RPC holder is a certificated pilot; someone who has only passed TRUST is not a certificated pilot, but may still be called a "pilot" as they are "operat[ing] the flying controls of an aircraft."

Yeah -- they're treating UAVs/RPVs as unmanned/remotely-piloted forms of existing categories/classes, instead of as a new category/class.

Just to add to the confusion, Australia's Civil Aviation Safety Authority use the term "UAV Controller".

In Australia.."controller" is a term which has been used (interchangeable with "pilot".)
The operator of an aircraft is the corporate body responsible for its "operation"..


text:
Are there any privately owned V-22 Ospreys?
Could someone buy a V-22 Osprey and convert it to a luxury interior rather than a military one? Has anyone done that? Are there any images available of a private Osprey made to be luxurious inside? What does the interior of the US President's Osprey look like?

There are no 'private' Ospreys thus far (all are operated by USAF, USMC and JSDF)- the Bell Boeing MV-22 Osprey used by the US Marine Corps's HMX-1 presidential helicopter squadron:

... will conduct presidential support missions, which means these aircraft will carry presidential support staff and news media representatives travelling with the president," the USMC says. "The Osprey mission at HMX-1 does not include carrying the President of the United States."

so I'm not counting on 'luxury' interiors. When (and if) a civil version of V-22 is produced (or if the Japanese feel like selling theirs), you can buy it and make the interior whichever way you like.

Or you could buy an Augusta Westland AW609, which is in flight tests at the time of writing this but expected to be available privately.


text:
What is the temperature of the air leaving the combustion chamber of a CFM56-5C?
What is the temperature of the air leaving the combustion chamber of a CFM56-5C? I was wondering as I could only find out that the fuel burns at around 1500 Celsius but this can't be the same as the air temperature because the air/fuel ratio isn't 1:1.

The air temperature will tend to reach the same temperature as the fire, and can easily be more than 1500 C.

What comes out of the combustor is a lot more than 'air', it consists of combustion products plus some unused oxygen and fuel, and nitrogen that didn't oxidize in the process. Its temperature should be mainly dependent on the flame temperature, minus whatever was lost on the (very short) way out.

Quick answer: At the design point considered, which is assumed to be takeoff conditions, a CFM56-5C combustor raises gas temperature to 1360°C (the share of the compressor in this raise is about 600 °C).
This is a common value found in modern turbine engines, a balance between fuel consumption reduction and turbine material capabilities (nickel super-alloy, more on that here and here).
Turbine entry temperature (TET) varies with thrust. Takeoff TET is maximal and top-of-climb TET is about 100°C less. Takeoff TET cannot be allowed for a long time, due to the damages which would be incurred by the high-pressure turbine guide vanes and blades.
Some details about turbine engine principles follow.

Station numbers
In turbine engineering, to facilitate description and comparison, steps in the Brayton cycle are identified by a station number.

(Source)
Additional stations are defined to reflect specific needs (e.g. for the cold flow of a turbofan). The full standard is known as ARP 755, see this old but free description.
The exit of the combustor (which is also the turbine nozzle guide vane leading edge) is station 4. In this nomenclature, Tn is the temperature at station n, Pn the pressure, etc. As an example, the sensor seen in the fan inlet of many turbofan engines is commonly referred as T12 or P12T12 sensor.
Gas temperature and entropy
Thrust which can be produced by the engine depends on the turbine inlet temperature (station 4), which is limited by materials.
There are two means of raising the temperature. The compressor raises the temperature by increasing air pressure, the combustor raises it by fuel combustion at (ideally) constant pressure. The later increases entropy due to the breaking of hydrocarbon chains.
This is visible on a so called temperature-entropy (T-s) diagram, e.g. this one for the CFM56-7B:

CFM56-7B T-s diagram. Source
We can see the compressor work between stations 0 and 3 (with no change in entropy in a perfect cycle) and the (ideally) isobaric raise in temperature and entropy between 3 and 4 as fuel chemical potential energy heats air.
The area under the curve is representative, along with the mass flow, of the net work of the engine (energy produced by the turbine minus energy consumed by the compressor), hence its efficiency. The area depends on two main factors:

How much pressure (and temperature) is raised by the compressor.
How much entropy (and temperature) is added by the combustor.

The goal is to achieve the desired turbine temperature with the highest efficiency. By increasing the pressure ratio of the compressor (the height of the left vertical segment) less entropy has to be added by the combustor (horizontal segment). This means less fuel.
There is a specific PR value, around 30-35, for which the area under the T-s curve is maximal. This value is indeed targeted by the engine designer. Looking at the previous diagram (oblique lines in kPa), we can see the PR used is around 30.
CFM56-5C
Four CFM56-5C were used to power the smallest A340. A340 manufacturing has been stopped, as 4 engines are no more a good option in the era of high fuel prices.
Your question indeed boils down to: What is T4 for the CFM56-5C?
From this document (in French):

Pour une approche analytique de la dynamique du vol

which is a thesis by Elodie Roux, this table on page 198:

tells us the T4 temperature is 1633 K, that is 1360 °C.

how did you find that, I also saw you found the plane with folding wings, how do you search these things so fast and accurately. I honestly think your advise could help the rest of my life! @mins

@SRawes It takes many years and great dedication, grasshopper, to learn the ancient art of Google-fu. Few have the fortitude to attain the level of skill of Master mins. We are all... his humble disciples. [bows low, gong sounds]

I shall dedicate my life to the art of Google fu and train it to work for my whim!  @TomMcW

I'm still in awe and seriously want to know how @mins

@SRawes: Try this query on Google. You're searching, in english, for CFM56-5C and T4, and do not want results for maintenance providers ("capabilities"). This answer is shown first, but quickly you'll see the relevant thesis from Elodie Roux. It depends on your search history as Google uses the history to customize results (if you searched recently for a chain saw, you may alas receive links for chain saw vendors during several months).


text:
Would a gimbaled, always horizontal cockpit be beneficial to fighter jets?
Would it be possible to have a spherical cockpit that was gimbaled in jets such as fighters so the pilot was always upright. With all controls in the cockpit wirelessly communicating with the rest of the jet?
Wouldn't this be an advantage as it would be easier to aim and the pilot wouldn't get disorientated and could see anywhere by maneouvering?

Aside from the other reasons in the answer, a spherical cockpit simply wouldn't fit inside most fighter jets. Even going back to WWII, it was a common saying that when flying a Spitfire, you didn't "sit in it", you "wore it" (in the same way that you wore your clothes).

@alephzero Didn't Biggles say something about "flying by the seat of your pants" when he first flew, because he had to keep repositioning himself on the wicker seat while flying, and that showed him he wasn't straight-and-level ?

The redout limit is only 2-3g, so forget pulling a complete 9g loop. Also, what if the enemy is below you? Can't flip over and take a look (although dogfighting is obsolete anyway). Such a design would be quite a disadvantage even if engineering wasn't a problem.

Unless you're intentionally flying uncoordinated for some reason (e.g. a slip) you ARE always upright.  WRT the G-force acting on you, that is, which is the important thing.

An interesting aside, if you have played the video game Battlefield 1, you can enable an option that allows the 3rd person plane view to remain horizontal as you described. I tried it after having the conventional setting for a couple weeks, and was amazed at how much harder it was to aviate. Obviously this is fully mental but I did notice much of what AirSick's answer mentions, even if it is only a video game.

With enough engineering (read, money), all sorts of things would be possible, but if you picture the aircraft in a hard, level turn, the g-forces would be pressing "down" relative to a conventional cockpit, but "sideways" for a cockpit that was gimbaled so the pilot was sitting upright relative to the horizon.  And that would probably be a lot harder to take than the usual "down" G-forces.  Resisting 9 G's pulling your hand and forearm straight down can be done with a support for your arm (side-stick controller) or a bit of a ledge at the bottom of the handgrip (side-stick or center stick), but keeping precise control of the aircraft with 9 G's pulling your hand sideways might be a lot harder.
Beyond that, the sideways G force would be pushing your head to the side, which probably ends up banging your helmet -- pretty hard sometimes -- against whatever restraint or canopy it meets.
Something that achieves some of the goals you mention is the "Virtual Reality" helmet of the F-35, where the pilot can essentially look through the airframe and "see" aircraft, targets, and whatnot even in places that he wouldn't have an actual line-of sight.  That allows him to look in any direction, reacting to threats, tracking his target, and so forth.  And without having to gimbal the cockpit.  Although for what the F-35's cost, that might actually be cheaper!

"Although for what the F-35's cost, that might actually be cheaper!" I'm reasonably sure the mechanics involved in creating a gimbaled cockpit would be so big and heavy that there would be no room for the other tricks the F-35 can do. The result would probably be less of a fighter than previous generation fighter planes.

How would this be 'easier'? The pilot would have no direct reference to the orientation of the aircraft. The upright pilot pulling back on the stick would expect the aircraft to pitch up. With the aircraft in practically any orientation the actual effect could be anything, including pitch down. How would you map the control inputs to the actions of the aircraft in a way that would make any sense to the pilot?

Could it not just be pulling up tells the computer you want to go up and it figured out what the jet needs to do? I was thinking you could be swinging the jet left to right yet your view not changing so you could aim at a target while moving in barrel rolls @airsick

@SRawes The problem with what you're describing there is it will make the pilots… well airsick: Having your view fixed while your inner ear is telling you you're moving is one of the things that can cause motion sickness, and since you're still moving with the fighter a gimbaled cockpit will set up exactly that kind of situation. Gimbaled cameras do make sense for, and are frequently used in, unmanned aircraft though, allowing the operator to maintain a fixed view or track a target independently of the aircraft's motion.

The OP's idea is actually building a machine to make an error that is often made by beginning student pilots, who instinctively lean their body or head to keep their view of the ground level when banking the plane, instead of maintaining a fixed position relative to the plane. When flying visually, getting conflicting information from "the seat of your pants" and from your eyes is not a good stragegy.

@voretaq7 although I'd guess that professional fighter pilots are likely to be pretty immune against or at least very used to effects inducing motion sickness.

While on second thought I remember reading something about even highly experienced seamen getting seasick from time to time...

+1 @SRawes I guess you mean the view always staying horizontally level, just pitching on the vertical axis?

The actual biggest issue with this is that in many maneuvers the pilot does NOT want to be upright, precisely because of the G forces involved.
In a fighter jet, a sudden nose down maneuver from level flight produces negative G forces - it causes the blood to rush to the head, producing a "red out", which is very painful and potentially lethal.
To counteract that, fighter pilots roll the aircraft so that its inverted (belly up to the sky, cockpit down to the ground) and then pull back on the stick to "climb" downwards.  This produces positive G forces on the pilot, forcing blood to rush into their lower limbs, triggering a "black out" - but the pilot can control this by use of their g-suit and various exercises to force blood back up the body.
So, no, you don't want the pilot to be level and upright all the time, often the pilot will deliberately make themselves not upright because its safer and more pleasant.

Using air pressure to squeeze the blood out of your legs and back into the rest of your body is a good thing. Using air pressure to squeeze the blood out of your head... no so much.

When maneuvers are executed, usually you want the resultant force to be exerted along the axis head-foot, like weight is exerted, because you already know how to fight weight / gravity, and this about all that you are able to do easily and safely.

Source.
In an aircraft, the aerodynamic force is (more or less) normal to the wings, even in a turn properly executed.
So it's more natural to continue to have the body normal to the aircraft floor than having it gimbaled and having a transverse force to fight against, poorly.


text:
Is a smart flight data recorder possible?
Let's consider the following scenario:
A flight is in trouble, the flight data recorder senses it(Anything the computer would sense and deem would result in an accident), it drains fuel from the tanks into its tank working with GPS to drain just enough fuel to take it to the manufacturers base, taking into consideration flight conditions, head wind or tail wind.  It detaches from plane before impact, opens up its 6 arms with drone rotor propellers, fires its batteries starts flying at speed, once it reaches rotation speeds, it spreads its fixed wings and fires its jet engines because fixed wing aircraft are more efficient than rotor wings, it then drops its heavy rotor wing powering batteries to save fuel and flies to its manufacturer's base.  It might even use jet engines to power it rotor wing phase
Version 2 would not detach but can cut itself out of the aircraft. If it senses water it will use its a compressed air tank that it will leave in the aircraft to inflate a rubber tube that will raise it to the surface floating so it can take off as a water plane/drone or rotor wing drone
Is a smart flight data recorder possible as described in this scenario?  What are the drawbacks or impediments?

the point is that we analyse data to find out what happened, because most often than not, that specific combination of factors never happened before, so, how would a computer "deem [that it] would result in an accident"?

if an aircraft is not doing what it should, ALL faulty systems become known to the computer because its connected to them if certain systems cannot be repaired and with known aircraft physics a computer can tell if it will result in a crash, the same way a simulator works... we do sometimes punch in unkown parameters into a simulator, situations that would result in a crash

an aircraft could be doing something that it should not do, and yet have no faulty system at all.

for your version 2: https://aviation.stackexchange.com/q/2536/1467 or https://aviation.stackexchange.com/q/50816/1467

@securitydude5 You seem to believe that a computer being connected to something makes that computer omniscient. That simply isn't the case.

Just because something is a bad idea doesn't mean it is bad to ask the question...

Read about deployable flight recorders, used on military aircraft, including the P-8 Poseidon (a.k.a. 737).

Your proposal is that the FDR should stop recording before the incident is over. Total non-starter.

Why would you use such a complex and failure prone system? Assuming you mean that you would fly the flight data recorder (FDR) to the base of the manufacturer. There a couple of drawbacks:

Flying the FDR before impact means that you miss vital information about the situation just before impact
The added weight of the construction means that you are flying around for years with lots of dead weight. Which is very expensive. Airlines are really interested in you if you can shave half a kilo of every seat. It would save them millions over the lifespan of the aircraft
FDR's are not decoded by the manufacturer but by specialized agencies such as the BEA and NTSB
Most crashed happen around take off and landing, so your smart system has to act fast
All FDR and cockpit voice recorders are made really strong so that they can survive the impact of the crash, in addition they are located at the back of the aircraft. They picked this location as the tail section remains the most intact in a crash. Latest generation FDR's uses solid states disks for storage, greatly increasing the resistance against impacts.

In addition to the other reasons Version 1 is a bad idea:

A drone that could potentially fly halfway around the world is very heavy, unless you put it right in the center of weight launching it would imbalance the airplane. You can't put it in the center of the airplane because you want people and stuff there, so it would have to go at one extreme or the other. The farther from the center of weight the greater the moment arm, detaching that weight will change the flight dynamics making a bad situation worse
It only makes sense if you have an ejection system for this drone, with explosive bolts and a rocket to get it clear. You can't just stick this anywhere, airplanes would have to be re-designed to accommodate it. That's expensive, and would eat into passenger and cargo space
Taking fuel from the tanks will take minutes, few emergencies give you that amount of time. Plus you're taking fuel that the airplane may need if it recovers. If it wasn't going to crash before it probably is now
There's a better alternative in the form of satellite communications which would stream CVR and FDR data without all the Rube Goldberg crashy-crashy stuff

Now let's talk about Version 2:

Having a data recorder cut itself out of a submerged airplane is probably detrimental to the survival possibilities of the occupants inside
If an airplane has ditched then it's unnecessary, if it has crashed into the ocean the chances of the cut-out mechanism being intact enough to work are extremely low. Even it it works it's very possibly trapped by debris
There's a better alternative in the form of satellite communications which would stream CVR and FDR data up to the moment of impact

Unfortunately, if the airplane is submerged and there are people in it, they're mostly going to die. I doubt the cut-out mechanism would really affect that: there's no reason it needs to open a hole into the passenger cabin and opening the doors to let people out will create much bigger holes.

Your version 2 comments are unfortunately all incorrect. Military aircraft have been using deployable recorders for years, precisely to aid in recovery of the aircraft during water crashes.

There's a huge difference in what the OP is proposing and deployable recorders, which are basically pods @user71659. I think deployable recorders make perfect sense, especially for ETOPS airplanes, it's the whole cutting itself out and then flying as a drone part that I have problems with.


text:
How many crew members load and offload luggage on an Airbus A380?
What are the standard ground needs of a modern double-decker airline.
How many crew members load and offload luggage on a modern double-decker airliner on any typical trip?

Surely, this will vary according to the policies and staff availability of the ground handling company.

Rephrasing it as "what are the standard ground needs of a modern double-decker airline" would make it fit the guidelines and lead to more interesting answers. How many people and how much coordination are needed to turn around a massive aircraft always impressed me.

@ymb1 i 100% agree with you about not being off topic but some people have a stricter interpretation of the rules that we do so before this good question gets killed I went looking for a fix :-)

It's a trick question... how many crew members load and offload luggage? none. The crew does not do that.

@CGCampbell True for the flight crew, perhaps. But there might be ground crew that does...


text:
Is water a possible fuel for jet engines?
Jet engines can run on almost any fuel, and the operating temperatures of modern jet engines' hottest sections are anywhere between 3000 and 3150 degrees F (1648 and 1732 degrees Celsius). Does that mean that a hydrogen on-demand system could work on modern jets?
Water is pumped and heated first by the exhaust section, then directed towards the hotter sections of the engine (when hot enough to not cause cooling and lower engine efficiency) where it's broken down into hydrogen and oxygen at a heat above 1472 degrees F (800 degrees Celsius), then those gases are pumped into the engine for combustion.
The advantages are that firstly, water is abundant and therefore cheap. Even sea water could be used because at those temperatures it's easy to design a system that would get rid of the impurities that would otherwise corrode critical engine parts.
Secondly, it would save on manufacturing costs given that non-heat critical parts in the exhaust section would not need to be made of sophisticated and expensive materials and alloys given the cooling effect of water.
Thirdly, the costs of the fuel weight would be reduced given that the energy density of hydrogen is twice that of fossil fuels, so less would need to be carried. And most importantly, the environment problem would be solved in aviation given that there would be little or no carbon dioxide emissions.

There is a very strong smell of "free energy" (or perpetual motion) scheme from your post. The energy required to break the atomic bonds will always be greater than the energy released on recombination due to losses in the cycle. This is basic thermodynamics.

This question is about chemistry, not aviation.  Let the chemists explain at length why you can't get energy from burning water.  If this sort of scheme could work, the primary beneficiaries of it would surely be electrical power plants, not aircraft.  But it can't work, it's "free energy".  Except that water is never fuel, it's ash from burning hydrogen (which by definition happens in the presence of oxygen).  VTC.

In other words: the amount you'd cool (and thus contract) the hot air, while breaking down the water, will be more than you can heat (and thus expand) it by burning the resulting hydrogen.

A much more feasible way is to heat the water into steam and use it to power another turbine. Then you don't need too high of a temperature, and you are also not consuming water but keep reusing it. Probably too heavy for aviation but already a thing for ground and marine turbines.

This should be asked over on https://physics.stackexchange.com/ (or maybe https://chemistry.stackexchange.com/). Not that the answer would be that different.

Um...water is not a fuel. It used to be a fuel (hydrogen) that has burned already.

@user3528438 you are still using fuel, and those turbines don't recirculate water unless they absolutely must.

@Federico Looks like a few people are enjoying themselves with answering this question...

The only way it could possibly be is the planet so hot that surroundings of the aircraft are well over the boiling temperature. Then the water would boil, producing steam that could power some machine.

Im glad this question was re opened I wonder who voted to get it reopened

@JanHudec It was now cross-posted to [chemistry.SE]: Is water a possible fuel for jet engines?

I'm sorry but I don't see how copying the least voted answer from chemistry.SE is helping you or how it would make the question better

As far as "why not" questions go, this is actually pretty clear because it explains 1) the supposed benefits of the technology and 2) it clearly and specifically explains the proposed mechanisms.  This makes is much easier to answer without having to guess why the asker thought it would work well.

No. Water is not a fuel, it is hydrogen that has burned already. It is a very stable oxidation product, so stable that it is used to extinguish fires. Commercial production of hydrogen is not done by heating water. From the wiki:

There are four main sources for the commercial production of hydrogen: natural gas, oil, coal, and electrolysis; which account for 48%, 30% 18% and 4% of the world’s hydrogen production respectively.[5] Fossil fuels are the dominant source of industrial hydrogen.

There is quite some interest in R&D projects to produce hydrogen from water, because like the OP states water is very abundant. Many production methods are researched: electrolysis, radiation, chemical reaction. Heat is one of the least promising techniques, since temperatures of up to 3000 °C are required. From this wiki:

Thermal water splitting has been investigated for hydrogen production since the 1960s.[16] The high temperatures needed to obtain substantial amounts of hydrogen impose severe requirements on the materials used in any thermal water splitting device. For industrial or commercial application, the material constraints have limited the success of applications for hydrogen production from direct thermal water splitting and with few exceptions most recent developments are in the area of the catalysis and thermochemical cycles.

And that is in a production facility in a research lab. Now we're going to do this in an aircraft, where safety, weight and reliability are of prime importance. Water has been used for propulsion before (by injecting it into the hot exhaust gas of a turbojet) but that went out of the door: it does very little for high-bypass engines, not enough to justify the extra weight.
But most inventions start with an outlandish idea which is dismissed by the grey eminences at first. The OP has two seedlings that may have merit:

Use waste heat that is produced anyway to generate useful power or thrust. This is done in power stations already: in remote communities in Australia one can find gas turbines driving alternators, next to a steam turbine that uses the waste heat from the gas turbine. But this is not viable for aircraft, too heavy and no redundancy since the steam turbine cannot work without the gas turbine.
Use water that is on board anyway for propulsion. Waste water from the toilets! Inject that into the hot exhaust gases for an environmentally friendly solution.

You're proposing to use the heat of the engine to break down water into hydrogen and oxygen, and then burn the hydrogen in the oxygen, turning it back into water. And, remember, when I said "the heat of the engine", I mean the heat you obtain by... burning the last lot of hydrogen and oxygen you made.
Even if this process was 100% efficient, you'd just be converting back and forth between water and hydrogen/oxygen. No energy would be created, so there'd be no thrust. And it's not 100% efficient: you'd lose energy, rather than gain it.

It also requires having something on hand to start the engines with and get them hot enough to crack the water in the first place, thus needing fossil fuels or a hydrogen storage system (with the associated weight penalties).

@FreeMan Yes, though that "just" requires equipment at airports, as long as you don't want to restart the engines in mid-air.

@FreeMan, that is pointless. If there was energy to be gained, anything else would be minor technical detail. But there isn't, so the minor technical details are not relevant.

If you could add the reason it is not and will never be 100% efficient (the Second Principle of Thermodynamics, nothing to do with insufficient technology like some perpetuum mobile inventors like to postulate) this would be an even more more complete and still succint answer.

@DavidRicherby has demonstrated how breaking down water, and then burning hydrogen back to recreate water is a process with losses that cannot generate a positive budget of energy. But let's go further, as if this was not the case, and see which quantity of water is involved.
(All figures are approximated to make them simple to compute mentally.)

Let's evaluate the quantity of water you would need to replace fuel, based on the energy that can be extracted from hydrogen and from fuel. We need to compare the specific energy of both.
For a familiar reference: 1kWh = 3.6 MJ, this is what would consume a steam iron in an hour.
To get 1 kg of hydrogen from water, you need to break down, in the most optimistic case, about 10 kg of water (atomic mass of $H_2$ = 2 , of $O$ = 16, of $H_2O$ = 18).

If hydrogen and oxygen could be separated, by some mean, 1 kg of water would produce 100 g of hydrogen. Hydrogen has a specific energy of 120 MJ/kg,  that is 12 MJ/100 g.
But the specific energy of fuel is much greater: 42 MJ/kg.

Assuming you have the water breakdown reaction for free, which is indeed not the case, you still need 42/12 = 3.5 kg of water to replace 1 kg of fuel.

Not really a good deal... the aircraft needs tanks about 3 times larger and needs a whole redesign to increase the maximum takeoff mass (which in turn will require a lot more hydrogen).

That's without counting fuel which, in real life, is needed to breakdown water and extract hydrogen. With this fuel you reach insane masses.
However... There are many processes for water splitting, some are really not very efficient... but if it's free...
The energy required to extract hydrogen could be solar energy, which you get for free. There is a process known as thermochemical cracking which use cells with catalyst materials exposed to solar rays.
This process is extremely slow and not very efficient (7%), but it works!
While this is not usable for aircraft propulsion, it's possible to use it for large scale solar energy storage, converting solar energy into hydrogen chemical energy which can be used later.
See Almeria Spanish solar power plant.

No, the energy density of water is plain and simple ZERO (as long as we stay in the realm of oxygen chemistry). Because to get a 1 kg of hydrogen from water, you have to provide all of those 120 MJ.

“assuming you have the water breakdown reaction for free” it is still whatever runs the reaction for you and not the water that has the energy.

There is absolutely no way “to be said” that you get any energy after breaking down water for the simple reason that you are starting with water and ending with water. Each substance has chemical energy and this energy depends only on the substance and not on how it was made. During reaction—any reaction—the difference in chemical energy between reagents and products is released (absorbed if negative). Since you are starting with water and ending with water, nothing can be released. The “free” reaction makes no sense and renders any other conclusion pointless.

And note that energy density is, per definition, just difference between chemical energy of the fuel plus oxidizer and the chemical energy of the oxidation products (well, there are some quirks about state of the products, but basically). Since water is already the oxidation product, it can't have any energy density.

@JanHudec: Yes, what you say is correct. Perhaps you could write an answer on the loss occurring when breaking down and recombining water components. But that's not the angle I've chosen, I'm on the mass of water vs. the mass of fuel.

"@DavidRicherby has demonstrated how breaking down water, and then burning hydrogen back to recreate water is a process with losses that cannot generate a positive budget of energy". True, but there is a large amount of waste heat.

@Koyovis: There is not a large amount of waste heat. The process is not self-sustaining. It's not even self-starting! If you added a battery, for example, to start the process it would quickly shut down. The waste heat would be supplied by the battery.

@mins, but you are comparing numbers that make no sense at all. If you actually did have that free decomposition, water would be infinitely better than kerosene, because you could run it through the cycle any number of times and get free energy. But since you don't, water is infinitely worse, because you can't get any energy out of it at all. The number for one non-existent cycle is useless.

@mins, actually, I don't care about the assumptions at all. I am saying that you are comparing two numbers derived in a way that makes their comparison meaningless.

@JanHudec: I say the quantity of hydrogen found in 3.5 kg of water can produce by combustion with oxygen the same energy than 1 kg of fuel? Is this wrong or correct?

@mins, it's irrelevant. Since you are starting with water and ending again with water, if you could get at least a tiny amount of energy from the cycle, you could get as much energy as you like by simply looping it. So that comparison does not explain why it wouldn't work.

@JanHudec: As you seem to agree, then you may also agree that if it were possible to extract energy from hydrogen in water, the quantity of water required would still be 3.5 kg for water vs. only one kg of fuel. This would create a problem for the airplane which would need to be redesigned. That's all I wanted to demonstrate: Even if hydrogen could be extracted, the mass of water would be ridiculous anyway. Now this is not in my answer, but for sake of completeness, it is possible to extract hydrogen for free using solar energy, but at a rate incompatible with the aircraft use.

@mins, but it wouldn't be ridiculous, because it would be possible to recycle the water.

@JanHudec: Good point. If we accelerate water vapor from the exhaust forward, towards the water splitters and burners, we should cancel some thrust from the hot flow. That could work for a turbofan though.

Based on your assumptions, and if it was possible to operate the engine at higher temperatures, would it then not be possible to substitue water as a fuel using  that one third of energy ratio to fuel ratio and still power the aircraft, given that fuel efficiency is much higher as engine operating temperatures go higher.  I remember when I was young, early in the 90s I saw a british program where a company had invented a mud like substance where its owner could melt copper on his hand.

@securitydude5: "if it was possible to operate the engine at higher temperatures" combustion of 1kg of fuel would still generate more energy than combustion of hydrogen in 1kg of water. "early in the 90s [...] invented a mud like substance [...] could melt copper on his hand": TV has always been very interested in showing "miracles", Uri Geller and the like who where able to bend spoons with their "telekinetic" powers. Producers knew it was deception but nurtured the legends. Money had (and still has) no smell.

True the goal is to equate the energy density per kg of water to fuel without the need to redesign the aircraft as you noted and because fuel is expensive and it produces greenhouse gases.  I was hoping the substance is mainstream and popular by now because it was a secret then and thats over 20 years ago.

@securitydude5: Burning hydrogen has never been a secret. Water vapor is a greenhouse gas, maybe worst than CO/CO2 due to the quantity. But burning hydrogen is not the same than burning water. Water is hydrogen already oxidized (burnt). You can't extract hydrogen from water with less energy than it can give back when burnt again, it's trivial chemistry. Those who are on the idea of conspiracy and free energy from water, just pretend not understanding all the terms of the equation to sell their books and conferences.

I meant the substance that was applied to the demonstrator's hand and he melted a piece of copper in his hand

There are two ways of get this working, but both seem only very remotely possible.

Venus planet, or any other with the surrounding temperature above the water boiling temperature. In such environment, liquid water would have energy: while boiling, it can produce compressed steam able to rotate a turbine. A compressor, similar to the compressor of the jet engine, could help getting more hot air into the system to boil the water. Same way liquid nitrogen may work on Earth.
There is plenty of nuclear energy in the water, it contains hydrogen that powers the Sun by fusing into helium. A machine the could use such an energy is currently being built while I think initially it will power more something like a large ship.

You cannot decompose the water into oxygen and hydrogen and then burn these components because exactly the amount of energy required to decompose is released during the later burning process. Due inevitable losses, the machine eventually will stop after exhausting the initial energy pool.